Environmental scientists are closely examining unusual developments in the Southern Ocean after a sharp decline in humpback whale sightings and the unexpected appearance of rare seabirds along Australia’s eastern coastline raised fresh concerns about the health of one of the world’s most remote marine ecosystems. While researchers have not yet established a direct cause, they believe persistent marine heatwaves and changing ocean conditions could be influencing the movement and behaviour of several marine species.
The first signs of concern emerged in late June when whale-watching operators in southwestern Western Australia reported seeing significantly fewer humpback whales during their annual migration. According to observers, whale numbers were estimated to be around 60 percent lower than what is normally expected during this period, prompting scientists to investigate whether environmental conditions may be disrupting the animals’ traditional migration routes.
Shortly afterward, birdwatchers recorded an unusually large presence of albatrosses and petrels off Australia’s east coast. These seabirds are rarely seen in such areas because they typically forage thousands of kilometres away in the colder waters of the Southern Ocean. Many of the birds spotted during the event were also found to be in poor physical condition, suggesting they may have struggled to find adequate food or had been forced away from their usual feeding grounds.
Marine scientists say these observations are concerning because both whales and seabirds depend heavily on predictable ocean currents, water temperatures and food availability during their long-distance migrations. Any disruption to these natural systems can affect breeding success, migration timing and survival. Researchers caution that while the unusual sightings may be linked to ongoing marine heatwaves, additional scientific evidence is needed before drawing firm conclusions.
Experts point out that although marine heatwaves are often associated with warmer tropical waters, they can also develop in the frigid Southern Ocean. Even a relatively small increase in water temperature can significantly alter ecosystems that have evolved under consistently cold conditions. Changes in ocean temperature can affect the abundance and distribution of krill, fish and other prey species that form the foundation of the food web supporting whales, seabirds and numerous marine predators.
Scientists have noted that a large and persistent marine heatwave has affected waters surrounding Australia’s Heard and McDonald Islands since February. These remote islands are internationally recognised for their rich biodiversity and lie close to Antarctica. In addition, the southern Tasman Sea has also experienced prolonged warmer-than-normal ocean temperatures since at least April. Researchers believe climate change is increasing both the frequency and intensity of such marine heatwaves, placing added pressure on sensitive polar ecosystems.
The unusual wildlife observations also come shortly after Australia confirmed its first case of highly pathogenic H5N1 bird flu in a migratory seabird. Although scientists have not connected the disease with the recent changes in whale and seabird movements, they say multiple environmental pressures could be affecting wildlife simultaneously and warrant close monitoring.
Researchers emphasise that many questions remain unanswered because the Southern Ocean is one of the least monitored marine regions on Earth. The remoteness and harsh conditions make it difficult to collect long-term ecological data, limiting scientists’ ability to determine whether the recent observations represent temporary anomalies or signs of broader environmental change. They stress that sustained monitoring of marine mammals, seabirds, ocean temperatures, currents and prey populations will be essential to better understand how climate change is reshaping Antarctic and Southern Ocean ecosystems.
